DURHAM, N.C. -- Zion Williamson tossed up an alley-oop lob for RJ Barrett, and on the next trip downcourt, Barrett returned the favor by setting up a dunk for Williamson.

For these high-flying Blue Devils, that No. 1 ranking sure seems to fit.

Williamson scored 21 points, Barrett added 20 and Duke routed Eastern Michigan 84-46 on Wednesday night in its first game this season as the nation's top-ranked team.

"It is great to be No. 1, but nobody really cares who's No. 1 right now," Williamson said. "The goal is to win a championship in March."

Javin DeLaurier and Jack White added 10 points apiece for the Blue Devils (3-0). Playing two days after leapfrogging Kansas for the top spot in the AP Top 25, they looked every bit the part of a top-ranked team.

They shot 47 percent, turned 20 turnovers by the Eagles into 31 points and took command with an early 21-1 run keyed by an assortment of dunks by Williamson.

Damari Parris had nine points to lead outmanned Eastern Michigan (3-1), which shot 31 percent and was stuck in single-digit scoring for about 17 1/2 minutes.

Unlike their last game -- in which Army hung with them for about 30 minutes three days earlier -- the Blue Devils took the drama out of this one early.

"Everything we did kind of worked," coach Mike Krzyzewski said, "but the reason it worked is because we played so hard."

Williamson put Duke up by 20 for good midway through the first half with the highlight of the night -- leaping so high to pull in a seemingly errant alley-oop pass that his armpits were even with the rim before he dunked -- and Barrett made it a 30-point game with a bucket with about five minutes before halftime.

"The atmosphere got the best of us the first 6-7 minutes of the game," Eastern Michigan coach Rob Murphy said. "It was a struggle for us to score in the first half, and once you get down in this building ... it's pretty hard to come back."